210 Mr. Phillips on a new Oxide of Manganese ; Sfc. 



printed in the Phil. Mag. for July and August last, he has 

 again mentioned, that during solution in sulphuric acid the 

 peroxide becomes protoxide; and as the result of further 

 examination, I readily admit the accuracy of his assertion. 



I employed in my first experiments, to the best of my re- 

 collection, the native oxide of manganese, which occurs, and 

 frequently in masses of great purity, in Warwickshire ; this 

 has I believe been regarded as the peroxide of the metal. On 

 repeating my experiments, I soon found, however, that it is not 

 constituted as the peroxide is usually admitted to be ; and in 

 prosecuting my inquiries, I discovered that it is a compound 

 of the metal and oxygen, which has not, as far as my researches 

 have extended, been hitherto noticed. This mineral is of a 

 gray colour, the tint of which is not remarkably different from 

 that of the well-known crystallized peroxide; it is, however, 

 less brilliant. It is much harder than the peroxide, does not 

 soil the fingers so much, and is lighter in the proportion of 

 4*283 to 4-819 : when reduced to powder and boi^td in water, 

 a trace of muriate of lime is discoverable. 



In order to determine the state of purity of the ore, 200 grs. 

 were treated with excess of muriatic acid, 0*64 of a grain, 

 evidently silica, remained undissolved ; sulphuretted hydrogen 

 gas passed into the solution of muriate of manganese, threw 

 down a dark-coloured precipitate, which, when washed and 

 dried, weighed 1*03 grain; this yielded a deep blue solution by 

 treatment with nitric acid and ammonia : it was therefore sul- 

 phuret of copper, and may be considered either to exist as such 

 in the ore, or as indicating ?n equal weight of the peroxide. 

 The excess of sulphuretted hydrogen ^eing expelled by heat, 

 the solution was colourless, and gave a perfectly white preci- 

 pitate with ferrocyanate of potash. 



I exposed 200 grains of the powdered ore to a strong red 

 heat in a covered platina crucible for an hour ; the loss of 

 weight was 26*55 grains, and the mean of three experiments 

 gave 26*52, or 13*26 per cent. As it is stated by Dr. Turner 

 and other authorities, that peroxide of manganese, similarly 

 treated, loses 12*122 per cent, I entertained no doubt that the 

 ore under exammation was peroxide ; for the difference of 

 1*14 might readily be attributed to error of operation and a 

 little accidental moisture. I next determined the quantity of 

 oxygen separable from the ore by solution in sulphuric acid ; 

 for this purpose, I put into a glass retort 2000 grains of sul- 

 phuric acid and 200 grains of the powdered ore ; the flame of 

 a strong spirit-lamp was applied until gas ceased to be 

 evolved ; the retort was then corked, and its mouth kept under 

 water until the sulphate of manganese was cold ; the water 



being: 



